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%I #2 Mar 30 2012 18:37:18
%S 1,9,84,935,12480,196623,3591560,74847168,1755406674,45804773872,
%T 1317004696656,41386864224420,1411592788770580,51942256939923051,
%U 2051313029747633376,86548588478842559964,3885584044838123386104
%N Column 2 of triangle A166900.
%C Triangle A166900 transforms rows into diagonals in the table of coefficients of successive iterations of x+x^2 (cf. A122888).
%o (PARI) {a(n)=local(F=x, M, N, P); M=matrix(n+4, n+4, r, c, F=x;for(i=1, r+c-2, F=subst(F, x, x+x^2+x*O(x^(n+4)))); polcoeff(F, c)); N=matrix(n+3, n+3, r, c, F=x;for(i=1, r, F=subst(F, x, x+x^2+x*O(x^(n+4)))); polcoeff(F, c)); P=matrix(n+3, n+3, r, c, M[r+1, c]); (P~*N~^-1)[n+3, 3]}
%Y Cf. A166900, A166901, A166903, A122888, A135080.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Nov 27 2009
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